Exploration Of New Infrared Nonlinear Optical Mateirals In Quaternary Chalcogenides Systems

Unfortunately, all of commercial IR NLO materials possess some insurmountable drawbacks, which severely impede their development. Hence, to explore the outstanding IR NLO materials have attracted much attention. This paper aims at designing excellent IR NLO materials. By introducing alkali metal, alkaline earth metal, transition metal and rare earth metal into the research system, a series of compounds with a non centrosymmetric structure were synthesized using a high-temperature solid-state reaction in evacuated silica tube and the properties of compounds also have been characterizated to evaluating their application prospect.1. BaCdSnS₄ and Ba₃CdSn₂S₈: Syntheses, Structures, Nonlinear Optical and Photoluminescence PropertiesBa CdSnS₄ and Ba₃CdSn₂S₈ were successfully obtained by the incorporation of the d10 transition-metal cations and alkaline-earth element into the framework. In their structures, isolated CdS₄ and SnS₄ tetrahedra as structural building blocks are connected to generate obviously different structures, respectively. For BaCdSnS₄, its structure can be characterized by the two-dimensional ∞[Cd-Sn-S] layers composed of Cd S₄ and SnS₄ tetrahedra, while in Ba₃CdSn₂S₈, the CdS₄ and SnS₄ groups are connected to form a three-dimensional framework, which is different to the 2D ∞[Cd-Sn-S] layers structure in Ba CdSnS₄. Moreover, the critical optical parameters of BaCdSnS₄ and Ba₃CdSn₂S₈ have been studied. Diffuse-reflection, IR, and Raman spectra show that their optical transparencies can cover the mid-IR range up to 25 μm, and both compounds exhibit good SHG responses, which indicate that the two compounds may be promising NLO materials for IR application. Furthermore, photoluminescence properties of Ba CdSnS₄ and Ba₃CdSn₂S₈ were investigated for the first time and results indicate they also have good photoluminescent properties. 2. Syntheses, Structures, and Nonlinear-Optical Properties of contained lanthanide sulfides LiA₃MS₇（A=Sm, Gd; M = Si, Ge） with a large laser damage thresholdLi Sm₃ Si S₇, Li Sm₃GeS₇ and Li Gd3 Ge S₇ were successfully obtained by the incorporation of the rare-earth elements and alkali metal into the framework. The three compounds are isostructural and crystallize in the polar hexagonal space group P63. In their structures, Li S6 octahedra are connected together to form a 1D ∞[Li S6] chains running parallel to the 63 axis, and are surrounded by isolated MS₄ tetrahedra. The ∞[Li S6] chains and isolated MS₄ tetrahedra are linked together by ReS8（Re=Sm and Gd） units to build the 3D network. In addition, because of the pure sample of Li Sm₃ Si S₇ are only synthesized at the present, its characterion is performed in this paper. The correlations of the particle size versus SHG intensity of powder Li Sm₃ Si S₇ indicates that the compound is not type-I phase matching at 2.09 μm radiation and its SHG intensities are about 12 times those of the commercial AGS in the particle size 38-55 μm. The compound also possesses a high powder laser-induced damage threshold of ～3 times that of AGS, which may suggest that it has potential applications under high power nonlinear optics. 3. A₄GaBiS₉（A=Sm, Gd）: the design, syntheses and structure for two contained lanthanide sulfides with noncentrosymmetric structureSm₄GaBi S₉ and Gd₄ GaBi S₉ were successfully obtained by the incorporation of the rare-earth elements and Bi3+ cations with lone electron pairs into the framework. The single-crystal structure determinations show that the two compounds are isostructural and crystallize in the noncentrosymmetric space group. Their structures are characterized by the one-dimensional ∞[Ga2Bi2S11] chains, which are connected togather via rare-earth cations to built the 3D network. 4. Synthesis, structures, and properties of two magnesium silicate fluorides Mg₅（SiO₄）₂F₂ and Mg₃SiO₄F₂Two silicate fluoride compounds, Mg₅（Si O₄）₂F₂ and Mg₃ Si O₄F₂, have been successfully synthesized and characterized. In their structures, it can be seen that they have 3D framework structures built up by Mg–O–F octahedra and isolated Si O₄ tetrahedra. The difference between two crystal structures is mainly induced by the different ligands of Mg atoms. The IR spectrum confirms the existence of the Si O₄ tetrahedron. Thermal analysis shows that Mg₅（Si O₄）₂F₂ has high thermal stability. It has been proved that compound Mg₅（Si O₄）₂F₂ is an incongruent melting compound. The UV-Vis-NIR diffuse reflectance spectrum shows that the experimental band structure is about 5.32 e V for Mg₅（Si O₄）₂F₂.